Select the false statement regarding the cardiac muscle contraction?
A) Initiation of cardiac muscle contraction is through fast opening of voltage-gated sodium channels.
B) The slight repolarization after the initial large increase in membrane potential is due to closure of voltage-gated sodium channels and transient potassium efflux through ungated potassium channels.
C) Slow calcium channels are responsible for the development of plateau phase in cardiac muscle contraction.
D) The fast repolarization after plateau phase of cardiac muscle contraction is mainly due to opening of delayed rectifier potassium channels.
E) The delayed rectifying potassium channels are responsible for the relative refractory period during early phase 4.
B) The slight repolarization after the initial large increase in membrane potential is due to closure of voltage-gated sodium channels and transient potassium efflux through ungated potassium channels.
(this part is incorrect)
it is due to closure of sodium
n opening of potassium channels... (the fast ones)
Ans is.......... A............. in cardiac muscle contraction its due to funny Na channel which are slow not fast voltage gated Na which is seen in skeletal muscle .............Happy-2
The phase 1 (overshoot) is due to closure of voltage-gated fast Na channels and the opening of iKto channels (transient outward K+ current). Depolarization produced by Na+ influx leads to activation of a transient outward current mainly carried by K+. This current is called ITO. As the activation of ITO is transient, only a brief efflux of K+ occurs, causing a brief and limited repolarization.
I'd say C is the right answer. Here goes my explanation-
phase 1 is due to closure of voltage gated Na channels and transient efflux of K via UNGATED channels, as depolarisation by then wd have already closed the VOLTAGE gated iK1(inward rectifying current) channels.
phase 2 developement is mainly dependent on the closure of these iK1 channels and also slow influx of Ca.
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